Knock control fluids have been developed to mitigate various abnormal combustion events in engine cylinders. For example, various combinations of gasoline, ethanol, methanol, other alcohols, water, washer fluid, and other inert fluids may be direct injected into an engine cylinder in response to an indication of untimely detonation.
One example approach for injecting a knock control fluid to mitigate cylinder abnormal combustion is shown by Surnilla et al in US 2012/029795. Therein, knock is addressed using one or more of spark retard (until a threshold point) and direct injection of a knock control fluid. The threshold point beyond which less spark retard and more knock fluid injection is used may be adjusted based on operating conditions and various cost functions (such as exhaust emissions, fuel economy, cost of operation, engine performance, etc.).
However the inventors herein have recognized that there may be potential issues associated with the use of the available knock control fluids. Specifically, the presence of ionic materials in existing knock control fluids can degrade engine performance. For example, a washer fluid (that includes a water-alcohol mixture) may be directly injected into the combustion chamber responsive to provide a desired amount of engine dilution to address engine knock. However, ionic materials typically introduced into the washer fluid by the addition of ionic surfactants (e.g., in the form of counter ions such as Ca2+, Na+, K+, Li+, etc.) can have an adverse impact on combustion chamber deposits, catalytic after-treatment materials, and exhaust system components. In addition, the washer fluid components can cause the release of unintended pollutants into the vehicle exhaust. While the ionic surfactants are added in low concentration to washer fluid, they are required in the fluid composition to both lubricate the wiper blades and to enhance the removal of foreign material from the surface of the windshield. Further, the ionic components are needed to buffer the washer fluid and to aid in the ionization and agglomeration of dirt particles during application of the washer fluid on the windshield.
Thus, in one example, the above issues may be at least partly addressed by a method for an engine comprising: in response to knock, direct injecting a fluid including one or more non-ionic surfactants into a cylinder from a reservoir coupled to a direct injector; and in response to operator demand, delivering the (knock control) fluid from the reservoir to a vehicle windshield. In this way, the windshield wiper fluid may meet wiping demands while also controlling knock, without degrading engine performance.
In one example, a windshield wiper fluid may be reformulated to include one or more non-ionic surfactants. The reformulation allows ionic materials, particularly alkaline and reactive materials, to be excluded from the windshield wiper fluid. The fluid may be stored in a reservoir (e.g., a secondary reservoir) coupled to a cylinder direct injector. In response to an operator demand for windshield wiping, the fluid may be delivered from the reservoir to the windshield. By replacing the reactive components of the fluid with organic buffers and non-ionic components, the critical washer fluid properties can be retained, allowing the wiper fluid to retain its wiping function. In response to an indication of cylinder knock, the same fluid may also be delivered to the cylinder. For example, the fluid may be direct injected to increase engine dilution and reduce knock. By replacing the ionic components of the fluid with non-ionic components, the risk of contamination of the combustion chamber and exhaust system with aggressive and recalcitrant metal salts is reduced. This allows engine performance to be improved and the life of exhaust components to be increased.
It should be understood that the summary above is provided to introduce in simplified form a selection of concepts that are further described in the detailed description. It is not meant to identify key or essential features of the claimed subject matter, the scope of which is defined uniquely by the claims that follow the detailed description. Furthermore, the claimed subject matter is not limited to implementations that solve any disadvantages noted above or in any part of this disclosure.